Abstract The hydrolysis equilibrium of salts, as a follow-up to chemical equilibrium and ionization equilibrium in high school chemistry, plays a significant role in establishing students’ understanding of equilibrium concepts. To deal with the misjudgment of color changes caused by adding hydrochloric acid to FeCl3 hydrolysis equilibrium (as described in textbooks), a series of experiments were conducted by replacing concentrated hydrochloric acid with concentrated sulfuric acid or nitric acid. It was found that adding one drop of concentrated sulfuric acid or nitric acid to 0.01 mol/L FeCl3 solution resulted in the fading of the yellow color, revealing the intrinsic color of hydrated iron ions:pale purple. Further experiments involving the gradual addition of concentrated nitric acid to 1 mol/L Fe(NO3)3 solution demonstrated that the solution color was influenced by the coordination between Fe3+ and NO-3. This investigation into the cause of the yellow color in FeCl3 hydrolysis equilibrium may provide valuable insights for potential revisions to textbook content.
ZHOU Ping, YU Juan-Juan, QUE Rong-Hui. Investigation on Cause of Yellow Color in Hydrolysis Equilibrium of FeCl3[J]. Chinese Journal of Chemical Education, 2025, 46(17): 89-94.
